Keywords: cooling medium, cooling, temperature, quenching oil, Vacuum, cooling mediu, heat treatment, austempering,

　　The cooling medium is usually mineral oil (mineral oil). Such as engine oil, transformer oil and diesel oil. Engine oil is generally No. 10, No. 20, and No. 30 engine oil. The larger the number of oil, the greater the viscosity, the higher the flash point, the lower the cooling capacity, and the corresponding increase in operating temperature.

　　High-speed quenching oil is quenching oil with increased cooling speed in high temperature regions. There are two basic ways to obtain high-speed quenching oil, the 1 is to select different types and different viscosity of mineral oil, to mix with each other in the appropriate ratio, by increasing the characteristic temperature to improve the cooling capacity of the high temperature zone; the other 1 is to add additives to the ordinary quenching oil, the formation of ash-like floating matter in the oil. Additives include barium salt, sodium salt, calcium salt, phosphate salt and stearate salt of sulfonic acid. Production practice shows that the cooling rate of high-speed quenching oil in the unstable zone of supercooled austenite is significantly higher than that of ordinary quenching oil, while the cooling rate in the low-temperature martensite transformation zone is close to that of ordinary quenching oil. In this way, high hardenability and hardenability can be obtained, and deformation is greatly reduced, which is suitable for quenching of alloy steel workpieces with complex shapes.

　　Bright quenching oil maintains a bright surface after quenching. The bright quenching oil with different cooling rates can be obtained by adding polymer additives of different properties to mineral oil. The main component of these additives is the brightener, and its function is to suspend the aging products that are not dissolved in the oil to prevent accumulation and precipitation on the workpiece. In addition, bright quenching oil additives also contain antioxidants, surfactants and coolants.

　　Vacuum quenching oil is the cooling medium used for vacuum quenching heat treatment. Vacuum quenching oil must have low saturated vapor pressure, high and stable cooling capacity and good brightness and thermal stability, otherwise it will affect the effect of vacuum heat treatment.

　　Salt and alkali bath quenching media are commonly used in grading and austempering.

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